This disclosure relates to sensor arrays and, in particular, to flexible sensor arrays.
During the deposition of image sensors on amorphous silicon thin film transistor (TFT) backplanes, a metal layer known as the contact metal/mushroom metal is used to contact a positive (p doped)-intrinsic-negative (n doped) (PIN) sensor to a TFT. In the case of flexible sensor arrays, this layer can cause undesired effects due to film stress and creation of electrical faults by contact with other metal layers.
The contact metal/mushroom metal is part of the connection between the TFT and the sensor. A via through an encapsulation layer over the TFT can connect the contact metal/mushroom metal to a TFT contact. The contact metal/mushroom metal layer can be disposed over the TFT. The mushroom metal shadows the TFT active region from light to minimize leakage current. However, this adds an additional layer between the TFT and the PIN sensor.
In the formation of a sensory array, after a TFT is encapsulated, an opening is formed in the encapsulation layer exposing a contact of the TFT. The mushroom metal is deposited over the encapsulation layer and contacts the TFT contact through the via. The n, i, and p layers of the PIN sensor are deposited on the mushroom metal. Accordingly, the creation of the connection between the TFT and the PIN sensor requires deposition and/or patterning processes separate from the TFT fabrication process.